1. Field of the Invention
The present invention relates to high-power flash lamp pumped, solid state lasers, such as those used for materials processing (e.g. drilling, cutting, welding, heat treating cladding, machining). Specifically, this invention relates to a new configuration of solid state gain medium, laser resonator, and flash lamp array which can provide significantly higher output laser power and beam quality than that possible from traditional solid state laser designs. The present invention describes a solid state laser which is principally defined by a hollow cylindrical solid state gain medium (glass or crystal), in contrast to conventional solid cylinder gain mediums or slab gain mediums.
2. Description of Related Art
In the past, as the solid state laser medium there have been known such media as the rod-like solid state laser medium and the slab-like solid state laser medium.
The rod-like solid state laser medium emits a laser beam when irradiated by a flash lamp surrounding the medium.
However, in such a device, when the diameter of the rod becomes large enough, heat that is generated during irradiation is accumulated in the interior of the rod, with the consequent drawbacks that not only the index of refraction becomes nonuniform within the medium but also that the rod itself suffers from mechanical stresses. In addition, when the diameter of the rod becomes too large, it leads to a problem that the excitation fails to reach the central portion of the rod with sufficient strength.
On the other hand, in the slab-like laser medium, both of the top and bottom surfaces of the slab are excited, for example, with the flash lamps as in the above, and at the same time, the laser beam that is excited is input and output via end surfaces of the slab that are cut with Brewster angle. In the laser medium, the excited laser beam is reflected between the top and bottom surfaces and propagates the whole length of the laser medium, so that the laser beam is free from lens effects and the efficiency of energy take-out is high.
However, in such a case the laser beam propagates through the medium by undergoing total reflection between the top and the bottom surfaces of the medium. Therefore, in order to maintain a satisfactory condition of oscillation, both surfaces have to be polished accurately, which leads to a problem that the fabrication requires a great amount of labor.